The E400 has quite a lot going for it, but one of the real show-stopping features is the ambient interior lighting. The system allows owners to adjust the tones using a slider that moves through the color spectrum, providing much more subtlety than what you might find in other vehicles, where the colors are pre-loaded. Owners of the E400 can also change the brightness and the intensity.

"The 'multicolor ambient lighting' feature, actually comes standard," I wrote in my recent review of the E400. "We settled on a luminous purple as our favorite, calling it an homage to Prince, RIP."

Benjamin Zhang/Business Insider

The Merc's ambient-lighting is just the latest example of a significant trend in luxury cars: creating a soothing and enveloping, customizable environment inside vehicles. To a certain extent, the trend has been influenced by smart devices and their numerous customization options.

The trend is trickling down into cheaper, mass-market cars and SUVs, but not with the same rich drama we enjoyed in the E400 Coupé.